Pneumatic tools



Patented Get. 3, 1961 3,082,495 PNEUMATIC TOOLS Qharles L. Babb, Dayton, Robert H. Alexander, Miamisburg, and Eugene Linsker, Dayton, Ohio, assignors to Buckeye Tool Corporation, Dayton, Ohio, :1 corporation of Ohio Filed Dec. 21, 1959, Ser. No. 361,953 9 Claims. (Cl. 121-34) This invention relates to fluid motors and more particularly to a fluid motor having an overspeed limit device.

Fluid motors, such as air motors for use in hand tools and the like, ordinarily have a governor for limiting the matimum free speed of the tool well within the safe tolerances and limits of the tool design and of a rotating device such as a grinding wheel fixed to the shaft of the tool. The governor setting for the tool may vary according to the type and size of the grinding wheel carried and the surface speed. Typical governed free speeds may be 4500 rpm. to 8500 r.p.m., while a typical free ungoverned speed of an air motor in a hand tool, running from a 90 psi. supply line, may be in the order of 15,000 r.p.m.

The governor mechanisms are made as reliable as possible, consistent with weight limitations and cost. However, they are subject to failure by conditions often beyond the control of the manufacturer of the tool. One such condition may be moisture present in the air supply line which condenses in the tool and then freezes while the tool is idle to jam the air governor. Also, rust, sediment or lack of proper lubrication may prevent the governor from closing properly. When this occurs, the tool may quickly overspeed before the operator can do anything about it. Since grinding wheels are usually tested to operate safely at a speed of only about 50% greater than their rated working speed, and since the centrifugal forces involved will increase in proportion to the square of rotational speed, it can be seen that an overspeed limit device must react positively and quickly upon the failure of the governor to prevent the disintegration of the grinding wheel or other object carried on the tool, or the destruction of the tool itself, with the risk of serious personal injury to the operator or to a bystander.

Accordingly, the present invention provides a fluid motor incorporating an overspeed limit device to disable the motor and to bring it to a safe stop in the event that the governor mechanism fails to operate. This is accomplished in this invention by a vane lock arrangement that provides for the inward movement only of the vanes within the rotor upon the occurrence of an overspeed condition. Centrifugally movable masses in the form of balls or the like are held in a normally inwardly detained or seated position in the rotor and are released upon the occurrence of a predetermined maximum angular velocity into engagement with the vanes providing for inward movement only of the vanes. This clears the vane track and causes the motor to stop even though fluid pressure, such as air, is maintained at the motor inlet.

It is therefore a primary object of this invention to provide a value type fluid motor as outlined above having an overspeed limit device that holds the vanes in an inner or non-operative position within the rotor upon occurrence of a predetermined overspeed condition.

Another primary object of this invention is the provision of a fluid motor as outlined above having a dependable overspeed limit device characterized by being self-cleaning, of simple construction, of positive operation, and easily resettable.

A further object of this invention is to provide a fluid motor as outlined above having a normally captive member held in a normal inner position and movable into an gagement with a vane to hold the vane in an inner position in the rotor upon the occurrence of excessive centrifugal force signaling excessive r.p.m.

Another object of this invention is to provide a fluid motor as outlined above having centrifugally movable balls or the like which are normally held within guideways or passages in an inner position within the rotor and which are centrifugally released and movable into camming relation with each of the rotor vanes providing for inward movement only of the vanes within the rotor, and thus locking each vane in a non-operative position as it slides into the rotor during movement past the motor discharge ports.

Other objects and advantages of the invention Will be apparent from the following description, the accompanying drawings and the appended claims.

In the drawings FIG. 1 is a partially broken away view of a typical hand tool incorporating a fluid motor which includes this invention; 7

FIG. 2 is a cross section through the vane type fluid motor taken generally along the line 22 of FIG. 1 showing the details of the overspeed device;

FIG. 3 is a view similar to FIG. 2 showing the overspeed device in the tripped or vane retaining position; and

FIG. 4 is an enlarged fragment of one of the vanes of FIG. 2 showing the ball retaining mechanism in enlarged detail.

Referring to the drawing, which illustrates a preferred embodiment of the invention, a hand tool constructed according to the teachings of this invention is shown generally at 1% in FIG. 1. The tool 10 broadly consists of a main body forming a cast motor housing 12 to which an operators handle 13 is attached. The housing 12 includes a sliding vane type air motor 15 with an output shaft 16 upon which may be carried a grinding cup Wheel 17. A stationary shield 18 mounted on the face of the housing 12 guards against accidental contact with the cup wheel 17.

The handle 13 is hollow to form an air inlet passageway 19 which may be connected to a suitable source of air under pressure, such as a flexible air hose not shown, by means of an air hose adaptor 20. An operators trigger valve is formed in the handle 12 and includes a trigger 22 operable by hand to turn a valve 23 rotatably mounted in the handle 12 in intersecting relation with the passageway 19. The rotation of the valve 23 applies air at operating pressure through an air inlet screen 26 to an air inlet core 27 formed within the interior of the housing 12.

The housing 12 includes a governor valve indicated generally at 30 interposed in the path of the air within the inlet core 27 for the purpose of governing the quantity of air supplied to the motor 15. The governor valve 30 includes a valve bushing 33 threaded into the housing 12 and within which a valve spool 34 and connecting stem 35 is longitudinally movable between the open position shown to a position overlying an outlet opening 36 formed in the side of the bushing 33. A valve spring 37 is positioned between the housing 12 and the valve spool 34 to urge the spool 34 in the open position shown, and is held in position by a guide pin 38 extending therethrough.

The motor 15 includes an outer housing forming a vane track cylinder 4.0 fitted into a cavity formed in the housing 12. The cylinder 40 has annular pairs of center ribs 42 and outer ribs 43 formed on the outside thereof to provide a sealing fit within the housing 15 and to provide inlet and outlet air passageways between the housing '12 and the cylinder 40. A motor inlet 45 is arranged through the cylinder 40 between the center ribs 42 and provides the means by which the air'from the outlet port 36 of the valve 3%) is applied to the motor 15. The

applied air between the center ribs 42 is under high pressure and is held from escape by O-rings 46 arranged in the housing in contact with the ribs 42.

Means forming vane track 47 within the cylinder in eccentric relation to the exterior configuration includes rotor 50 rotatably carried within an eccentric bore within the cylinder 40 on a pair of ball bearings, one being shown at 51. The axis of rotation of the rotor 50 is made to coincide with a center axis to the exterior of the cylinder 48 with the rotor having a running clearance fit with vane track 47 in the space between the inlet port 45 and a series of outlet ports 52. The outlet ports 52 are formed through the cylinder 40 on either side of the center ribs 42 and communicate with an outlet core 53 formed within the housing 12. Air exhaust means is provided by a deflector 55 which receives the spent air in the outlet core 53 and discharges it into the atmosphere adjacent the grinding wheel 17.

Vanes 69 are slidably received in vane slots 61 formed within the rotor 50 as shown. It is common practice to form the vanes of machined laminated phenolic material in the interest of making as light weight a rotor as possible. The vane slots 61 are shown as being arranged in offset relation to the center of the rotor 58 in a manner often referred to as a swastika vane arrangement. However, any suitable vane and slot arrangement may be used. The rotor 50 is formed with an axially disposed opening 63 and includes an axially extending tip 64.

Means for operating the valve 30 includes a governor body threaded into the tip 64 for rotation therewith. The operating mechanism connected to the governor valve 30 includes the body 65 and a pair of centrifugal flyweights 66 pivoted on pins 67 for rotation therewith. The weights 66 operate to move an axially disposed plunger 70 having a stem portion 71 extended through the body 66 into the passageway 63 of the rotor 50. A nut 72 is threaded on the end of the stem 71 and is adjustable to compress a regulating spring 74 positioned between the nut 72 and the body 65. The centrifugal outward movement of the weights 66 about the pins 67 causes a longitudinal displacement of the plunger 70 in a direction away from the rotor 50 against the resistance of the spring 7 4.

The head of the plunger 70 is formed in a cup 75 and contains a race of ball bearings 76. A rocker arm 77 is pivoted on a pin 78 for transmitting the axial motion of the cup 75 to the stem 35 of the valve spool 34. The arm 77 includes a pivoted link 79 in contact with the cup 75 at the bearings 76 for substantially frictionless engagement with the cup 75 to transmit its axial motion to the valve 34.

As the governor 30 is normally open in the idle position and is closed by the centrifugal force of the weights 66, the inclusion of an overspeed limit device is necessary to avoid the occurrence of a dangerous overspeed condition should the valve 30 fail or otherwise be prevented from functioning. The overspeed device of this invention consists of. a vane lock arrangement which provides for inward movement only of the vanes 68 upon the occurrence of an overspeed condition, retaining the blades in their retraeted or non-operative position in the rotor, effectively cleaning the vane track 47 to reduce to zero the displacement of the motor 15.

As seen in FIGS. 2 and 3 and in the enlarged fragment of FIG. 4, the rotor 50 is provided with generally radially extending passageways 80 in oblique intersecting relation with each of the vanes 60 in the rotor 50. Means defining a centrifugally movable member in each of the passageways 80 includes a ball 82 normally detained inwardly of the vane at the bottom of the passageway 80. The bottom of the passageway 80 is separated from the vane slot 61 by a wedge-like portion 84 of the rotor 50, and thus defines a ball seat.

Means in the passageway 80 retaining the balls 82 in the normally detained or seated position includes a spring biased detent member in the form of a ball 85 which is seated in the bottom of a relatively shallow drilled and tapped passageway 86 which opens at its bottom into the passageway 80. A portion of the detent ball 85 protrudes into the passageway 80 above the ball 82 and is movably urged into this protruding relation by a compression spring 87. A threaded screw plug 88 is threaded into the exposed end of the passageway 85 and may be adjusted with respect to the rotor 50 to adjust the compression force of the detent ball 85 against the ball 82.

The detent ball 85 normally holds the ball 82 in the first inward detained or seated position at the bottom of the passageway 80 against the portion 84. The ball 82 is centrifugally movable in the passageway 80 past the detent ball 85 from this first position to a second position in camming relation against the side of the vane 60 upon the occurrence of a predetermined maximum angular velocity of the rotor 50. Actually, the arrangement is such that the centrifugal force upon the detent ball 85 tends to assist in the release of the ball 82, providing for the centrifugal outward movement of the ball 82 against the vane 60. This escape velocity of the ball 82 may be adjusted by suitably adjusting the plug 88 against the spring 87. The vanes 60 are provided with steel inserts 89 forming a locking surface for the balls 85 in the cammed position.

The angular velocity, at which the balls 82 can be set to release by the adjustment of the plugs 88, will be above the free governed speed, and may be conveniently set about 30% above the nominal free governed speed, as an example, in the manner indicated. This provides a margin of 20% within the 50% maximum tested speed of the grinding wheel 17.

The camming of the balls 82 in the passageways 80 against the sides of the vanes 60 provides for inward movement only of the vanes as the vane track 47 is swept upon the revolution of the rotor 50. The vanes 60 are therefore held in the non-operative position clear of the track 47, and irrespective of the continued application of air pressure at the motor inlet 45, the rotor 50 will cease to be driven. It has been found desirable to use as many balls 82 as there are vanes 60, since a fluid vane motor can continue to operate on one extended vane. The efiiciency may be much less, but the displace ment remains until the withdrawal of all of the vanes into the rotor 50. It may be desirable to close the exposed ends of the passageways 80 by plugs 90, in order to maintain a good fluid seal about the entire surface of the vanes 60 in the rotor 50, where, in high performance fluid motors, the loss of fluid sealing area even on the low pressure side of the vanes contribute to loss of motor efiiciency.

It is expected that the overspeed limit device should go for extended periods coextensive with the life of the tool without being called upon to operate, but it must be immediately operable at any time, and free from the effects of such conditions that may cause governor failure. Accordingly, the balls 82 and 85 are preferably formed of stainless steel so that they may remain in the seated position over such an extended period without oxidizing into contact with each other or with adjacent portions of the rotor 50. The balls 82 and 85 receive some oil wetting through the vane slots 61 by lubricating oil normally fed into the air inlet passageway 19 by a suitable oiler in the air fed line. However, this lubrication is not depended upon nor required to assure freedom of operation since the lack of proper lubrication is one factor which may cause failure of the governor mechanism, and the balls must then be free to operate. Since rotors are inherently selfcleaning and dirt which may otherwise tend to collect is thrown off during operation, the overspeed limit device of this invention is also free from the effect of collected sediment that may otherwise tend to impair the operation of the tool.

sweater It is' necessary to disassemble the tool inord'er to reset the balls 8-2 in the rotorafterthey liav'ebeeirreileased-by a governor failure: However, this-is preferred to an'automatic reset arrangement iir'that it is desirable, if" not necessary, to tear the'too-l'down to ascertain and correct the causeoflthe attempted-'overspeedi Thereset operation consists of removingthe rotor 50" and depressing the balls 82*by means of any-suitable tool'i'nsertedin the passageways 86' to their"Bottom"seated positiomhe neath the detent balls 85. In case it is-not convenient nor desirable to remove the plugs 89 the rotor 50 maybe jarred to free the balls 82' fro rntheir cammed relation against the vanes 60. The vanes may then be removed from the rotor and a suitable instrument inserted through the vane slots 61 to contact and depress the balls 82.

It is therefore seen that the invention provides a fluid motor with a simple and fool proof overspeed limit device which operates to disable the fluid motor upon the occurrence of an impending overspeed condition.

While the form of apparatus herein described constitutes a preferred embodiment of the invention, it is to be understood that the invention is not limited to this precise form of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

1. A vane type fluid motor comprising means defining a vane housing having a fluid inlet and outlet, a vane carrying rotor mounted for rotation in said housing defining a vane track between said housing and said rotor, a vane slidably carried in said rotor and movable for sweeping said vane track upon the application of fluid pressure at said inlet efiecting the rotation of said rotor, and a movable member in said rotor operable in response to a predetermined maximum angular velocity to move into coacting relation with said vane providing for only inward movement of said vane in said rot-or to clear said vane track of said vane.

2. A vane type fluid motor comprising means defining a vane housing having a fluid inlet and outlet, a vane carrying rotor mounted for rotation in said housing defining a vane track between said housing and said rotor, a vane slidably carried in said rotor and movable for sweeping saidtvane track upon the application of fluid pressure at said inlet for effecting the rotation of said rotor, and means defining a centrifugally movable member in said rotor having a normally inwardly detained position and releasable from said position for movement outwardly into engagement with said vane upon a predetermined maximum angular velocity of said rotor providing for only inward movement of said vane in said rotor to clear said Vane track.

3. A vane type fluid motor comprising means defining a vane housing having a fluid inlet and outlet, a vane carrying rotor mounted for rotation in said housing defining a vane track between said housing and said rotor, a vane slidably carried in said rotor and movable for sweeping said vane track upon the application of fluid pressure at said inlet for effecting the rotation of said rotor, and means defining a movable member in said rotor having a normally inwardly detained position in relation to said vane and centrifugally movable from said position outwardly into camming relation against said vane upon a predetermined maximum angular velocity of said rotor providing for only inward movement of said vane in said rotor to clear said vane track.

4. A vane type fluid motor comprising means defining a vane housing having a fluid inlet and outlet, a vane carrying rotor mounted for rotation in said housing defining a vane track between said housing and said rotor, a vane slidably carried in said rotor and movable for sweeping said vane track upon the application of fluid pressure at said inlet for effecting the rotation of said rotbr, and a hall in said rotor movable-intoengage nient with said' vane u'po'n a predetermined maximum angular velocity of said rotor providing for o'nly inward movement'- of saidvane-imsaid rotor to clear said vane t'racle providing for the free: passage of fluid from said inlet-'to said outlet. a

5. In-a vane type fiuid' motor having a vane housing including a bore therein andhav-ingla fluid inlet and a fluid: outlet in predetermined angularly spaced relation opening'intosaid bore, avane carrying rotor mounted for rotation in said b'oreabout an-axis p'arallel to the axis of said here defininga space'tlierelietween, avane reciprocably carried in said rotor for contact with the walls of said bore to react with pressure fluid supplied to said inlet and to sweep said space in a direction toward said outlet producing rotation of said rotor, a movable member in said rotor operable in response to centrifugal force to move into coacting relation with said vane for providing a retaining force acting on said vane to ailow only movement thereof inwardly of said rotor, and means responsive to a predetermined maximum angular velocity of said rotor normally holding said movable member in a non-operative position and responsive to attainment of said maximum angular velocity by said rotor to release said movable member for acting on said vane.

6. A vane type fluid motor comprising means defining a vane housing having a fluid inlet and outlet, a Vane carrying rotor mounted for rotation in said housing defining a vane track between said housing and said rotor, a vane reciprocably received in said rotor and movable for sweeping said vane track upon the application of fluid pressure at said inlet for effecting the rotation of said rotor, means in said rotor defining a generally radially disposed passage in intersecting relation to said vane, a ball radially movable in said opening in an inwardly disposed relation with respect to the intersection of said passage and vane, means in said passage normally retaining said ball in a radially inward position and operable upon the occurrence of a predetermined angular rotor velocity to provide for the outward movement of said ball under centrifugal force into camming relation against said vane providing for inward movement only of said vane in said rotor to clear said vane track.

7, A vane type fluid motor comprising means defining a vane housing having a fluid inlet and outlet, a vane carrying rotor mounted for rotation in said housing defining a vane track between said housing and said rotor, a vane reciprocably received in said rotor and movable for sweeping said vane track upon the application of fluid pressure at said inlet for effecting the rotation of said rotor, means in said rotor defining a generally radially disposed passage in intersecting relation to said vane, a ball movable in said passage from a first position in inwardly disposed relation to said vane to a second position in cammed relation against said vane providing for inward movement only of said vane, and ball retaining means normally holding said ball in said first position and operable upon the occurrence of a predetermined angular velocity of said rotor to release said ball for centrifugal movement into said second position.

8. A vane type fluid motor comprising means defining a vane housing having a fluid inlet and outlet, a vane carrying rotor mounted for rotation in said housing defining a vane track between said housing and said rotor, a vane reciprocably received in said rotor and movable for sweeping said vane track upon the application of fluid pressure at said inlet for eflecting the rotation of said rotor, means in said rotor defining a generally radially extending passage in oblique intersecting relation with said vane, a mass movably received in said passage from a first position in inwardly spaced relation to said vane to a second position in cammed relation against said vane providing for inward movement only of said vane, and retaining means normally holding said mass in said first posit-ion and operable upon the occurrence of a predetermined angular velocity of said rotor to release said mass for centrifugal movement into said second position.

9. A vane type fluid motor comprising means defining a vane housing having a fluid inlet and outlet, a vane carrying rotor mounted for rotation in said housing defining a vane track between said housing and said rotor, a vane reciprocably received in said rotor and movable for sweeping said vane track upon the application of fluid pressure at said inlet for effecting the rotation of said rotor, means in said rotor defining a generally radially disposed passage in intersecting relation to said vane, a ball movable in said passage from a first position in inwardly disposed relation to said vane to a second position in cammed relation against said vane providing for inward movement only of said vane, and adjustable spring biased detent means positioned in interposed relation between said ball and said vane for retaining said ball in said first position and movable upon the occurrence of a predetermined angular velocity of said rotor to release said ball for movement into said 10 second position.

No references cited. 

